Nowadays, more cars are being added to the roads, which increases the risk of deadly accidents and the average commuter's daily travel time. To address these issues, vehicular ad hoc networks (VANETs) were developed, facilitating communication both among vehicles and between vehicles and infrastructure. Due to the great mobility of vehicles, the primary issue in VANETs is the requirement for very short communication latency, particularly for applications related to safety. Moreover, security is a significant concern that arises from Because nodes share sensitive information with one another about themselves and their surroundings. The infrastructure-based elements defined as roadside units (RSU) were formulated to overcome this problem by allowing information to be transmitted amongst vehicles, which could then be used to increase system safety and efficiency. However, in order to achieve certain desired Quality of Service (QoS), such as service coverage, throughput, reduced latency, or energy consumption, there are primary obstacles that arise when implementing (RSUs). These obstacles include performance issues, data security during transfer, and overall cost considerations. This article introduces a thorough survey of Roadside Units (RSUs) in VANET networks, providing an examination of the current research trends in this field. The survey explores the strengths, weaknesses, specific scenarios, methods, topologies, and potential future improvements of RSUs. Additionally, the paper focuses on three key aspects of RSUs: deployment, management, and security, analyzing their prominent features, motivations, challenges, methodology aspects, real datasets, metrics, and performance measures.